If you're going to strike up conversation with strangers, it's best if you make it easy for them. If you're asking for a joke, you're making it easy on yourself and setting a bar for them. I'm a jokester but I don't have a good repertoire of jokes on hand -- I respond to banter. So if you ask me if I have a joke, I often just sputter and throw out the last bad pun somebody shared with me.

Make a joke yourself, if you're feeling funny. But be warned... a stranger once asked me why I was going on a trip. I was visiting my dad who was presently in surgery for cancer that would go on to end his life. I was too emotional to answer with anything but the truth. I certainly wasn't going to respond well to humor.